The proposed research is designed to detect and measure the development and persistence of antibodies to different virus diseases, and following virus vaccines, and in the IgM, IgA and IgG classes of immunoglobulins by advanced methods of indirect immunofluorescence. This rapid and simple one step procedure is preferable to previous methods employing physico-chemical techniques such as sucrose gradient centrifugation and column fractionation followed by conventional antibody tests. Indirect immunofluorescence using liver tissue obtained at biopsy as antigen and serum of infectious or serum hepatitis patients will be employed in the search for hepatitis virus as an adventitious agent and its antibody. Preliminary results obtained suggest that certain types of fluorescent antibody reactions were associated closely with the core antigen of hepatitis B (HBcAg) and other types of stain probably represented surface antigen (HBsAg).